Definition
An aircraft electrical power unit that combines a constant-speed drive (CSD) and an AC generator into a single sealed housing, mounted on the engine accessory gearbox. The CSD portion uses a hydromechanical transmission to convert the engine's variable input speed into a constant output speed, which drives the generator to produce AC electrical power at a stable frequency (typically 400 Hz).
Plain English
A single unit bolted to the engine that makes the aircraft's AC electrical power. The engine's speed varies in flight, but this unit smooths that out so the electricity it produces stays at a steady, usable frequency.
Context Anchor
Seen in turbine aircraft electrical systems, engine accessory sections, maintenance procedures, and cockpit electrical system messages.
Derivation
"Integrated" because two devices that used to be separate — the constant-speed drive and the generator — are now built together as one unit. This integration saves weight, space, and plumbing compared to the older separate-CSD-plus-generator arrangement.
Why Pilots Care
Reliable electrical power is essential for operating avionics, flight instruments, and other critical systems during flight.
Intuition Check
Do not think of an IDG as only a generator. The key idea is that it integrates the generator and the speed-controlling drive in one unit.
Example Sentence 1
The IDG on the number two engine was removed for overhaul after a low oil quantity indication appeared on the flight deck.
Example Sentence 2
During engine start, the pilot monitors IDG output to confirm proper electrical generation.